Tyndall, John, 1820-1893 · London : Longmans, Green · leaf 95
strument. The double syren, as it is called, isnow before you, fig. 29 (next page). It is composed oftwo of Doves syrens, c and c, one turned upside down.You will recognise in the lower syren the instrument withwhich you are already acquainted. The discs of the two • It is hardly necessary to… … THE DOUBLE SYREN. 75 syrens have a common axis, so that when one disc rotatesthe other rotates with it. As in the former case, thenumber of revolutions is recorded by clockwork (omittedin the figure). When air is urged through the tube fthe upper syren alone sounds; when urged through t, thelower…
Sound
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